The present invention relates to a synthetic resin made bottle, and more particularly to a blow molded bottle having a specified panel design for absorbing a stress caused by pressure-reduction in the bottle with its uniform deformation.
Recently, as vessels for soft drink or the like, there have been commonly used synthetic resin, for example, polyethylene terephthalate made blow molded bottles (so-called PET bottles).
The bottle of this kind is filled with a liquid filler which is previously heated, for example, at 85.degree. C. for pasteurization, being sealed, and is cooled. At tills time, the volume of the liquid filler is reduced by the cooling, resulting in the pressure-reduction in the bottle.
The pressure-reduction in the bottle is liable to deform the wall of the barrel portion of the bottle. To prevent the deformation of the wall, it may be considered to increase the wall thickness of the bottle for enhancing its strength. This method, however, is inconvenient in increasing the amount of the molding material for the bottle, thereby bringing a rise in production cost.
To prevent the deformation of the bottle without the above-mentioned inconvenience, there have been made a variety of attempts of providing a panel on the barrel portion of the bottle. In general, such a panel has been designed to be formed with irregularities or ribs for adsorbing the attraction caused by the pressure-reduction in the bottle and for providing a strength against the deformation.
As one example of the above attempts, there has been proposed a bottle in Japanese Patent Laid-open No. sho 62-52032 by the present applicant.
In this example, the barrel portion of a bottle has a recessed panel surface falling in from the surroundings, wherein the recessed panel surface is reinforced with horizontally crossing reinforcing ribs. With this construction, the recessed panel surface uniformly falls inside the bottle accompanied by the pressure-reduction in the bottle, and the reinforcing ribs function to suppress the excessive falling and hence to prevent the deformation of the bottle.
The bottle with the conventional panel design has a considerably high strength; however, in the field of the synthetic resin made bottle, particularly, of the PET bottle, there has been demanded a blow molded bottle having further higher strength in compliance with the difference in the size and shape of the bottle.
In particular, the PET bottle can be molded to be extremely thinned depending on the material property, but it encounters such a problem that the strength of the bottle is reduced with a decrease In thickness.